A cool front will cross the forecast area from northwest to southeast this evening...with an associated wind shift and falling temperatures and dewpoints as the boundary passes through concurrent with sunset. The airmass ahead of the front is very unstable and there is a possibility of thunderstorm development late this afternoon and evening. However...mesoanalysis indicates warm temperatures aloft are suppressing convective initiation thus far as confirmed by a distinct lack of cumulus development in satellite imagery. High resolution models are picking up on this and generally developing few if any storms across our area...with most activity remaining over Wisconsin and far eastern Iowa through the evening. Have maintained isolated thunderstorms ahead of the boundary in the outgoing forecast...as if they do initiate the coverage should be spotty. However...despite the low probability and coverage any storms that do form have the potential to be strong to severe given the degree of instability present...with hail and wind being the threats. Once the boundary and any storms sweep out to the south/southeast early tonight cooler and quiet weather should prevail into tomorrow morning.

Active weather pattern will set up for extended after a brief break in precipitation chances. Boundary pushing south through Iowa today will continue to push south into Missouri...keeping conditions dry early Monday. Models have begun to come into good agreement with much of period...though NAM appears to be most aggressive and precipitation heavy...and have therefore trended towards GFS/European model (ecmwf) blend. Boundary lingering in the Missouri River valley will push east into Iowa late Monday...bringing chances for precipitation to the southwest. This system will push east. However...expect precipitation trends to continue to push northeast as wave lifts into Iowa through the day Tuesday setting up prolonged periods of precipitation chances as northwesterly flow persists across area as ridge across west begins to slowly shift east. Generally expect to see only periods of precipitation...though timing of waves is difficult at this time. Best chance for heavy rain will come Tuesday night across the south as low pushes east. Best moisture transport will be very near Iowa/MO boarder and may push south into Missouri. Currently models indicate precipitable water values near 1.6 inches in the south...which is relatively high for August. This will be followed by another round of uncertain timing on precipitation chances with large upper low pushing across Canada finally breaking down ridge and pushing east by end of week...bringing a break in precipitation chances for the end of the period.

With northwesterly flow aloft temperatures will be cool for the period...general below normal for early August. Do not have high confidence in such cool temperatures...given uncertainties in timing of precipitation chances in the extended...and have bumped temperatures up a few degrees...especially early in the period. However...feel highs in the 80s is a good trend for much of period...with cooler temperatures possible late in period.

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Aviation...03/00z issued at 708 PM CDT sun Aug 2 2015

Rain showers/thunderstorms and rain will accompany a cold front in southern Iowa as it slides southward this evening. Some brief MVFR/IFR visibilities/ceilings are possible in the stronger storms. Behind the front...winds will be northwest. VFR flight rules are expected during the balance of the taf period.